unexpectedly found nil while unwrapping an Optional value? - ios

Question

I'm facing with an error: "unexpectedly found nil while unwrapping an Optional value"
when I insert new data in coreData and reload my tableview, I recall this function
var unique = [String]()
var loadMovie = [String:[Movie]]()
func insertMovie(movie : Movie) {
let genre = movie.genre!
if unique.contains(genre) {
loadMovie[genre]!.append(movie)
} else {
unique.append(genre)
loadMovie[genre] = [movie]
}
}
and fetch data:
func fetchAndSetResults() {
let app = UIApplication.sharedApplication().delegate as! AppDelegate
let context = app.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "Movie")
do {
let movies = try context.executeFetchRequest(fetchRequest) as! [Movie]
loadMovie.removeAll()
for movie in movies {
insertMovie(movie)
}
} catch let err as NSError {
print(err.debugDescription)
}
}
and the app crushes for the error mentioned above on line: " loadMovie[genre]!.append(movie)" but if I reload app, my data are stored and visible in tableview. What's the problem?

Answer 1

you unwrapped optional variable means you just resolving the compile time error only. In swift you unwrapping the variable means it is represents that variable won't get the nil.You are just telling to the compiler .But now you are getting the nil (Run time Error) you need to handle this by using Optional Binding.
if let movies = try context.executeFetchRequest(fetchRequest)
{
loadMovie.removeAll()
}

Answer 2

Your variable loadMovie is a Dictionary with Strings as the keys and Arrays of Movies as what is stored for each key. If you are getting the error "unexpectedly found nil while unwrapping an Optional value" for line " loadMovie[genre]!.append(movie)" it means without a doubt the String called genre is sometimes not a stored as a key in your loadMovie Dictionary.
Use the code below to first make sure you can get the Array stored for that key (stored in the genre string), and if you can't then print out the String so you can debug, to find out what key is missing.
var unique = [String]()
var loadMovie = [String:[Movie]]()
func insertMovie(movie : Movie) {
let genre = movie.genre!
if unique.contains(genre) {
if let genreArray = loadMovie[genre]{
genreArray.append(movie)
} else {
NSLog("The missing genre: \(genre)")
}
} else {
unique.append(genre)
loadMovie[genre] = [movie]
}
}
Anytime you want a value that could be nil (not there) you can use the if/let pattern above. So for your second question in the comments you could replace return loadMovie[genre].count with:
if let genreArray = loadMovie[genre]{
return genreArray.count
} else {
return 0 // zero because there are no items
}
There are other ways too. You should checkout a good basic swift tutorial like: http://www.tutorialspoint.com/swift/
If you look at the section on optionals this should all be more clear. Here at stack overflow you are generally expected to first have tried to find out answers for yourself, and understand the basic theory. Unfortunately, that is why you are getting so many down votes. I hope this has helped.
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